The overall objective of this research proposal is to better understand the biochemical nature and the physiological significance of the receptors for prostaglandin Es (PGEs) and for human chorionic gonadotropin-luteinizing hormone (HCG-LH). To this end, experiments will be designed to (1) solubilize and purify PGE and HCG receptors to study their true biochemical nature as well as to raise antibodies to pure receptors. (2) to assess the physiological significance of these receptors by the use of antibodies to receptors and by measuring hormone binding and consequences (adenylate cyclase activity and progesterone synthesis) of this interaction in various reproductive states, and (3) to establish quantitative and qualitative relationships between hormone (which includes HCG as well as PGEs) binding and consequences of this phenomenon. The use of luteal tissue from cows in early pregnancy and from superovulated rats, or rats in various reproductive states, will provide us with greater flexibility and convenience in accomplishing the stated goals of this proposal. The solubilization and purification studies, besides giving information on the true biochemical nature of the receptors, can also easily test the possibility that PGEs and HCG bind to two different sites on the same receptor molecule. Raising antibodies to pure receptors, and using such specific antibodies in physiological studies would be a novel approach towards understanding of several potentially important biological phenomena. It would be a equally novel approach to try and block luteal function at will using specific antibodies to receptors. This proposal also takes a look at whether the target tissue responsiveness to PGEs and HCG is regulated by the availability of the receptors and/or decrease in efficiency in intramembranous coupling of receptor binding and activation of adenylate cyclase. Therefore, in summary, the experiments proposed here attempt to answer some basic questions regarding the mechanism of action of PGEs and HCG in corpus luteum which will also be pertinent to the area of membrane receptors in general.